The machines for the production of ice cream and those for the production of crushed-ice have different peculiar features, although having as a common concept the treatment, in a cooled environment, of a liquid alimentary mix to obtain a solid product. In fact, for the production of Sicilian style crushed-ice a slow freezing is required under relatively minimal intense stirring, at temperatures not excessively low, so as to obtain ice sufficiently large crystals. In the manufature of ice cream, on the contrary, rapid cooling, intense stirring and low temperatures are necessary, in order to obtain crystals which are as small as possible.
From the above it will be evident that it is a problem to furnish a single machine for both productions.
From the (Italian) Patent for Utility Model No. 193504 a combined machine is known for the manufacture of ice-cream and of crushed-ice in which two distinct motors are used for the operation of the stirrer, that is a motor at high speed, for the manufacture of the ice-cream, and a motor at low speed (a few rotations per minute) for the manufacture of the crushed-ice.
The duplication of the motors renders the machine rather complicated and costly.
It is further known from the Italian patent application No. 21216 A/88 to use refrigerating units operating with capillary tubes for the production of crushed-ice. In fact, the refrigerating units permit a kind of more mild refrigeration which is more suited for the production, compared with the more drastic condition employed for the production of ice-cream.